892 OLDER MESOZOIC FLORAS OF UNITED STATES. 
leaves, and, indeed, this latter doubtless took place much as it does in 
living cycads, the leaves always forming a crown to the trunks and 
falling away as the trunk elongates, leaving only their persistent bases 
to form a false bark. These are not wholly dead, but manifest vege- 
tative activity, and doubtless have some physiological function. The 
development of copious ramentaceous hairs would form a protection 
to the trunk both from cold and from violence. 
Something analogous to this may be seen in living cycads and in 
tree ferns; also in some palms, and a similar function is sometimes 
performed in other ways, as by the coat of wax on the wax palms. 
At any rate, we are confronted with the fact that Cycadella developed 
an exuberant growth of fine scales or hairs from the bases of its old 
petioles below the apex, which formed a woolly or mossy covering of 
considerable thickness, sufficient when tightly appressed to the trunk 
and petrified there to form a layer 5 to 15 mm. thick all over the fossil 
trunks. 
As already remarked, there is usually a clean line of separation 
between the armor proper and this outer covering, but if the latter 
consists of ramentum there must be points at which it crossed this 
boundary and reappeared in the superficial layer. Such points are not 
easy to find in the collection, but the fractured surfaces of a few speci- 
mens reveal the process of transition in a more or less imperfect way. 
Such specimens were carefully searched out and the most promising 
cases were sectioned and the surfaces polished. Slides were also made, 
and the whole process is as fully illustrated as the nature of the 
material will permit. 
The following is the description of the new genus Cycadella and 
the species distinguished in the collections examined: 
Genus CYCADELLA Ward.* 
Pl. LXX. 
1900. Cycadella Ward: Proc. Wash. Acad. Sci., Vol. I, p. 263, pl. xiv. 
Trunks relatively small, bulbous, subspheroidal, or subconical, vari- 
ously compressed, incased in a layer 5 to 15 mm. thick of dense tissue, 
consisting of the chaffy ramentum exuberantly developed from the 
leaf bases and extruded from the armor, massed and matted in the 
fossil state so as to form a thick outer covering to the trunk; leaf 
bases always filling the scars, occasionally caught inthe meshes of the 
outer coating, but normally truncated below, and constituting, with 
the ramentum walls, a dense armor 1 to 5 cm. thick; otherwise as in 
Cycadeoidea. 
Pl. LXX merely illustrates the nature of the ramentaceous chaff and 
the great length that it attains, but it would be obviously impossible 
1 The systematic position of Cycadella is the same as that of Cycadeoidea (see supra, p. 302). 
